Evaluating the Limping Child: Consider the Diagnosis of Lumbar Plexopathy

An 11-month-old girl presented to the emergency department (ED) with a 1-week history of upper respiratory infection symptoms and an intermittent fever (maximum temperature of 40°C, documented on a previous ED visit during the same illness course). The girl also had a 5-day history of a right-sided limp and refusal to bear weight.

Physical examination findings were significant for an externally rotated right lower extremity, with a refusal to bear weight and crying elicited on passive movement. The right lower extremity also had reduced power and strength and decreased range of motion compared with the left side. There was no bony deformity, no point tenderness, no visible erythema, and no sensory deficit.

On admission, results of a complete blood count with differential and a complete metabolic panel were normal, including levels of acute-phase reactants. Blood culture results were negative for bacteria and fungi. Radiographs showed the bilateral lower limbs and hips to be normal, with the exception of some inflammatory changes. Hip ultrasonography results also were normal.

Orthopedics service was consulted, and a diagnosis of transient synovitis was made. The child was discharged after an uneventful 3-day hospital course.

On subsequent follow-up visits to her primary care pediatrician, the girl continued to have asymmetry of the right leg compared with the left side, along with an inability to walk. Additionally, she was found to have generalized hypotonia, especially of the lower limbs. She had an asymmetric crawl and cruised by dragging her right leg.

Over the course of the next few months, orthopedics and neurology specialists were both consulted numerous times. Bony deformities of the right foot, peripheral neuropathy, and congenital benign myopathies were ruled out. Meanwhile, now at 16 months of age, the girl still had not walked independently and continued to have hypotonia with a right-sided limp.

Further imaging studies, including medical resonance imaging (MRI), eventually led to the diagnosis of lumbar plexopathy, and the patient was treated conservatively.

Evaluation of a Limping Child

Limp has a broad differential diagnosis in the pediatric age group. It is a common complaint in childhood, accounting for 4 in 1,000 pediatric ED visits. The cause of limp usually can be determined by way of a careful history and physical examination. Imaging studies often are necessary to confirm clinical suspicions, but diagnostic procedures rarely are required.

Classification of a limp can be based on sex: Limping secondary to trauma and trauma-related conditions (eg, Legg-Calvé-Perthes disease, toxic synovitis, tibial osteitis, groin strains) is observed more commonly in boys than in girls. Certain congenital conditions (eg, congenital hip dysplasia) and some systemic illnesses (eg, rheumatoid arthritis, systemic lupus erythematosus) that are associated with limping have a female predilection.

A child’s age is one of the most helpful factors in narrowing the differential diagnosis of a limp. Toddlers aged 1 to 3 years are ambulatory and active but have immature gaits and thus are prone to falls, typically with a torsional component. Infections also play a major role in limps in this age group, with immaturity of the bony cortex as the predisposing factor. 

Causes of limp in a toddler can include infectious or inflammatory processes (eg, transient synovitis, septic arthritis, osteomyelitis), trauma (eg, toddler’s fracture, stress fractures, puncture wounds, lacerations), neoplasm, developmental dysplasia of the hips, neuromuscular disease, cerebral palsy, and congenital hypotonia.

Children aged 4 to 10 years are more boisterous; this carries the risk of high-energy injuries such as fractures, dislocations, and ligamentous injuries. Microtrauma to the vascular supply of the femoral head is thought to be a cause of Legg-Calvé-Perthes disease, a common cause of limping in this age group. Infections are the foremost cause of limp in this age group; terminal vessels in the metaphysis of growing bones are a common site of infection. Moreover, rheumatoid conditions and neoplastic lesions such as leukemia and Ewing sarcoma begin to manifest at this age.

In children older than 11 years of age, the bony architecture is more mature and resilient, and muscle strength also has increased dramatically. A slipped capital femoral epiphysis is one example of how bone maturation, strength, and weight mismatches can lead to limping.

Arthritis, sexually transmitted infection (with associated arthralgia and arthritis), and neoplasms can present as a limp in adolescents. Other causes of limping in this age group are juvenile rheumatoid arthritis, trauma, leg-length discrepancy, and neoplasms such as osteosarcoma.

When evaluating a child presenting with a limp, the history should include questions about the presence of fever, chills, and other constitutional symptoms. Malignancies, infectious arthritis, osteomyelitis, Kawasaki disease, Henoch-Schönlein purpura, and juvenile idiopathic arthritis (JIA) all can present with a limp.

Questions about the time of day when symptoms are exacerbated should be included in the history. Early morning stiffness could be the first indication of JIA. Nocturnal pain suggests the possibility of osteoid osteoma or other bone neoplasms. A recent history of symptoms of upper respiratory tract infection suggests transient synovitis, while a remote history of upper respiratory tract infection could be a clue to an undiagnosed and untreated streptococcal infection predisposing to poststreptococcal reactive arthritis.

The pain associated with muscular and ligamentous strains, bruises, and injection sites can cause a child to limp. Back pain might be associated with diskitis. Joint pain could be referred pain. Pain that is aggravated by activity might be associated with overuse syndromes, stress fractures, or hypermobility syndrome, while pain that diminishes with activity suggests an inflammatory etiology such as arthritis.

Signs of weakness, paresthesia, or incontinence suggest neuromuscular involvement. Easy bruising, weight loss, or bone pain can be seen in association with neoplasm or other infiltrative disease. A history of urethral discharge suggests a genitourinary tract abnormality; vaginal discharge might point to a diagnosis of pelvic inflammatory disease. Testicular pain in boys also can present with an associated limp.

Our patient’s limp was attributed to a diagnosis of right lumbar plexopathy. It is unclear whether the girl’s condition is idiopathic or congenital. Differentiating this relatively rare clinical condition from other neuromuscular conditions among the pediatric population can be a diagnostic challenge.

Lumber Plexopathy Anatomy

The lumbar plexus originates with the anterior primary rami of the L1, L2, L3, and (in part) L4 spinal nerves and frequently with a contribution from the T12 spinal nerve (Figure). It is located within the posterior aspect of the superior and middle portions of the psoas major muscle.

The lumbar plexus supplies sensation to the skin overlying the pubic symphysis, some of the external genitalia, the anteromedial and posteromedial thigh, and the medial and anteromedial portions of the lower leg. Its motor components innervate the iliac muscle, the psoas major and minor, all the muscles of the anterior and medial thigh.

Because the lumbosacral plexus is situated within the protection of the axial skeleton, blunt trauma is a relatively uncommon cause of injury—an exceptionally violent trauma is required in order to damage the nerve plexus.

Etiology

Lumbar plexopathy can be idiopathic or congenital. In the pediatric age group, the causes of lumbar plexopathy mainly are structural diseases or disorders. These can include injury resulting from extrinsic compression, along with local or metastatic malignant disease such as lymphoma, carcinoma, sarcoma, sacral chordoma, or the nerve sheath tumors commonly associated with neurofibromatosis type 1 (isolated nerve sheath tumors initially might be asymptomatic, with gradual progression to pain and paresthesia).

The etiology of pediatric lumbar plexopathy also can be abscesses and hematomas affecting the pelvic and gluteal region; infections such as with Epstein-Barr virus; and vascular complications such as aortic aneurysms and their repair.

Clinical Features

Acute pain in the lower extremity usually is the first symptom of lumbar plexopathy, followed by weakness of the pelvic girdle leading to limping and refusal to walk. Muscle atrophy results if symptoms persist for a long period. Patients may have a variable sensory loss. Gait abnormalities and lower extremity edema might be seen, especially with bilateral lesions. The iliopsoas muscles commonly are involved, and patellar reflexes are diminished.

Complete recovery is the general rule, but mild weakness and atrophy can persist, and the process can take a few months to years.

Diagnosis

Plexopathy is a clinical diagnosis based largely on the history and physical examination findings. Computed tomography (CT) and MRI scanning can be used to confirm clinical suspicion by identifying any bony or soft tissue lesion compressing the plexus and delineating the injury to the nerve plexus and surrounding structures. Electromyography (EMG) can be helpful in demonstrating muscle activity and denervation of muscles that are innervated by one or more major nerves.

Treatment

The optimal treatment of lumbar plexopathy depends on a variety of factors, including the cause, location, severity, and duration of the lesions. Most traumatic plexopathies improve spontaneously, at least to some extent, and therefore are usually treated conservatively. 

Occasionally, surgical repair is attempted, which tends to yield better results. In general, if surgery is performed on patients with lumbar plexopathy, it is for the treatment of damage to blood vessels or soft tissues rather than to the neural elements.

Immunotherapy is being considered for the treatment of idiopathic lumbosacral plexopathy among adults with possible immune-mediated inflammatory changes, although no evidence from randomized, controlled trials supports any recommendation on its use.

Although a limp in a child can be a benign finding, it is necessary to differentiate its etiology from among a number of serious causes that can be associated with significant morbidity and mortality. Lumbar plexopathy, although rare, should be among the differential diagnoses under consideration in a child with a chronic limp and associated muscular atrophy, such as in the case of our patient.

Bhargavi B. Kola, MD, is an assistant professor and assistant medical director of the Department of Pediatrics at Texas Tech University Health Sciences Center at the Permian Basin in Odessa.

References

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6. van Eijk J, Chan YC, Russell JW. Immunotherapy for idiopathic lumbosacral plexopathy. Cochrane Database Syst Rev. 2013;12:CD009722.